Spelunky Invicible - A Nutz Mod is a modified version of Spelunky that contains cheats, mostly for generating weapons and items and deleting shopkeepers.
The current version is v1.0. Download Here
Press F11 while playing the game to bring up the dialog box.
Enter any of the following cheats (all letters should be small caps):
Don't worry about typing something wrong, it won't break your game.
Shopkeepers can be deleted by pressing F12.
You can discuss and contribute to this mod on the official Spelunky forums